Fate of Heat-Shocked Salmonella enterica and Escherichia coli O157:H7 Cells on Under- and Adequately Cooked Pork Gyros Trimmings During Postcooking Storage Until Serving
Year: 2025
Type: article
Abstract: • Heat-shocked cells of both pathogens showed increased thermo-tolerance vs. controls at 57°C. • In adequately cooked gyros, HS E. coli O157:H7 survived better vs. controls at 30 and 40°C. • HS Salmonella showed no additional cross-protection, regardless of temperature. • Post-cooking storage can permit pathogen persistence or recovery in adequately cooked gyros. This study assessed the fate of heat-shocked cells (HS) of Salmonella enterica and Escherichia coli O157:H7 during subsequent post-cooking storage of under- and adequately cooked pork gyros at 30°C (under broiler) and 40°C (in heating chambers), conditions usually applied in grill houses before serving. Frozen, semi-cooked gyros trimmings (2‒3 mm thick) were used. Undercooked gyros was derived from thawing (30 min at room temperature) (a w 0.950 ± 0.010; pH: 6.21 ± 0.13), and adequately cooked samples followed the package instructions (microwaved at 700 W for 2 min) (a w 0.808 ± 0.032; pH: 6.20 ± 0.09). Individual strains of pathogens were heat-shocked at 47.5°C for 60 min; controls were non heat-treated cells. Afterwards, cells’ heat tolerance was checked at 57°C by estimating inactivation rates ( k max ; min -1 ). HS showed lower k max (4−8 fold for Salmonella; 3−11 fold for E. coli O157:H7) than controls (p<0.05), indicating increased heat resistance. Thereafter, HS Salmonella or E. coli O157:H7 composites were surface inoculated (3.5‒4.0 log CFU/g) on under- or adequately cooked gyros and stored at 30 and 40°C for 6h (n=6) to evaluate “cross-protection” associated with a w changes that occur during storage. Controls were inoculated with non-HS cells. In undercooked gyros at 30°C, E. coli O157:H7 population levels (controls and HS) did not change (p≥0.05) after 6 h. In adequately cooked gyros stored at 40°C (a w 0.808‒0.829), HS E. coli O157:H7 persisted, whereas the controls declined, resulting in 1.8 logs higher than controls (p<0.05). Salmonella controls remained close to initial levels at 30°C (under- and adequately cooked) and 40°C (adequately cooked) or increased by 0.8‒1.1 logs at 40°C (undercooked) (p<0.05). HS Salmonella showed no additional cross-protection despite the recorded gyros’ a w (0.808‒0.829). Such findings may emphasize that even adequately cooked gyros can permit pathogen persistence or recovery during post-cooking short-term storage and until serving.
Source: Journal of Food Protection
Language: English
Subfield: Biotechnology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,300
OpenAlex ID: W7117150325